This invention relates to pharmaceutical compositions containing florfenicol as the active ingredient, and particularly to injectable compositions having a high concentration of florfenicol.
Florfenicol [D-(threo)-1-p-methylsulfonyl phenyl-2-dichloroacetamido-3-fluoro-l-propanol] is a known antibacterial agent and is useful for veterinary purposes. When treating a large animal, it is sometimes desirable to administer a composition having a high concentration of florfenicol. The large amount of florfenicol thus administered should then preferably exhibit constant blood levels and be active for a prolonged period of time.
Florfenicol has low solubility in water, about 1.3 mg/ml, and the preparation of a concentrated aqueous injectable solution is not practicable due to the large volume required to administer a therapeutic dose.
Florfenicol also exhibits low solubility in many pharmaceutically acceptable organic solvents such as 1,2-propanediol, glycerin, and benzyl alcohol.
Florfenicol is generally soluble in aprotic polar solvents, such as N-methyl-2-pyrrolidone or 2-pyrrolidone; however, concentration of these solvents at levels greater than 30% was found to cause injection site irritation and tissue damage upon intramuscular administration.